I tend to work exclusively from the theater. Besides the basic prep stuff, I tend to do a lot of meetings (Production Management, Scene Shop, Costume Shop, Props, Sound, etc), but also, since I tend to work on bigger shows, I have a larger staff. And I think the prep week is extremely important part of the team building process. I want to learn how the team works before the stress of rehearsal begins. Also, I like to keep work at work and home at home.
The best thing about being a resident PSM, is that I can quickly go through the basic prep stuff (I have all the paperwork and change names, add new people, etc . . .), so I tend to try to make prep week a 5 day, 40 hour thing, so I can take an extra day off . . . I often find the only "down time" I have away from 60 hour rehearsal weeks is prep week when I am in control of my own hours. If I am working at a new theatre, I would say I average about 50 hours for pre-production. BUT, the thing is since I am a resident PSM at a theatre, tend to start prep for shows up to a year in advance . . .
I do have a pretty comprehensive pre-production list.
I e-mail actors, but always follow up with a phone call. One, to make a personal contact, but also follow, answer any questions, and just start that personal relationship.